Natural disasters have an effect on many important economic and social parameters and are related to a wide spectrum of sciences. Their kind, form, scale, intensity and other characteristics vary in different areas on Earth. One of the most common fields where such disasters are of great importance (either as threats or as resulting damage) is the urban environment (either the buildings or the infrastructure). The complexity of the natural disasters concerning each of the five phases in their lifecycle (prevention, mitigation, preparedness, emergency management, recovery) leads to the selection of strong and most capable tools, in order to predict their results, i.e. the damage. Since nowadays the geospatial technologies have undergone an effective shift to become better suited to the internet, the most appropriate tools for this purpose are the Web-based GIS. In this review paper, a Web-based GIS, which is under development, named SyNaRMa (Information System for Natural Risk Management in the Mediterranean) is being presented. SyNaRMa features include collection and analysis of data related to earthquakes, landslides and forest fires, simulation of natural disaster effects resulting from realistic scenarios and prediction of their impact on the natural and anthropogenic environment of the wider implementation areas. It is to be noted that its open architecture offers many benefits and conveniences for future plans as for example the incorporation within the system of data related to other natural disasters (e.g. drought, desertification, tsunamis, volcanic eruptions etc.) and the potential to be used all over the world.